THE WATER FLEAS (CLADOCERA) 



36 (37) Head not helmeted; eye close to margin. . Daplmii longispina profn-r 



There are numerous varieties of D. lon^ispina pr()iH.T; <lciR-n<linK on i.rot».>rtion of v .1 

 The head may be large or small, its ventral marKin struiKht, com ave. or • onvcx Th.- ■ 

 have a large pigment with few lenses embedded in it, or it may be small.r with nutn. 

 jecting lenses. 



Found in all regions of the United States. 



37 (36) Head helmeted and eye therefore removed from margin. lsu;illy 



more dehcate and transparent than 36. 



Daphnia longispimi var. hyalina Leydig 1H60. 

 D. longispina var. hyalina varies conspicuously and greatly in the form and sizt- of the irr»t 

 and of the ventral and dorsal margins of the head, which may be concave, convex, or slraixhl 

 with any form of crest. The crest may be small and rounded (var. hyalina lypica). cxtcmlcil 

 into a broad semi-elliptical form (form mendotac); more or les.s triangular, with an acute |Mjint 

 in front (form galeata); which may be extended into a short spine. .\n indehnitc numljcr ol 

 other forms are present, some of which have been studied and describe<l. but not namc«l by 

 Entemann. The form of the crest in specimens from any one lake is fairly uniform 'ihouxh 

 2 varieties may be present), changing with the season, being larger in summer than in s|>rinic. 

 Adjacent lakes may vary greatly. Deep water forms usually have ^mailer (rests than ihine 

 from the shallow surface water. All varieties found in open water of lakes, in all parts ol ihe 

 coimtry. 



Figs. 1070, 107 

 38 (35) Ocellus absent 



Daphnia longispina var. hyalina. A and B. form typica. 

 D, form galeata. 



0.2 MM . 



C. furni mcndolac. 



head helmeted. 



Daphnia loni^ispiiia var. lougircmis Sars 1S61. 

 Valves broadly oval; spine long and slender. Head small and rounde<I with crest, .\ntcnnac 

 very long, reaching well toward posterior margin of valves when rellexed. Lenut h. 9 • t" • ^ '"'p- 

 This is the only representative of the European cuculUita groui) as yet sc-cn in this count r>-. No 

 doubt other forms will be discovered. Indiana; Wisconsin, in deep water of lakes in soulhcro 

 part of state; in surface waters in northern part. 



Fig. 1072. Daphnia loniircmis. 



